This invention relates to extensible and retractable pipe joints or connections, and more particularly to adjustable pipe or nipple structures such as drop nipples for automatic fire-extinguishing sprinkler systems, riser nipples for lawn sprinklers and the like. Heretofore various types of telescopic, adjustable pipe joints or assemblies have been proposed and produced, intended for uses such as with lawn sprinklers, automatic overhead fire extinguishing sprinkler systems, etc. In general, these prior devices were intended for a specific initial construction, as part of an original structure or lay-out of job. In such cases the required sizes and dimensions were completely predetermined, and the components of the adjustable joint were therefore pre-cut according to the specifications of the particular job. In the case of lawn sprinklers, the adjustable riser nipple would be installed before backfilling, and the adjustment then readily effected according to the level of the land. Thus, adjustment normally presented no problem.
In the case of remodeling of building structures employing automatic sprinkler systems, however, the installation of a false or acoustic ceiling made it necessary to cut and install longer drop nipples for the sprinkler heads. This was a tedious and time-consuming job, and represented a costly part of the work or installation. Efforts have been made to reduce the time and work involved, by the use of extensible pipe joints, but these were not satisfactory due to difficulty of on the job repair, because of the possibility of leakage, and also because the adjustment member in many instances was located above the false or acoustic ceiling, between the latter and the original ceiling. Such latter condition was inconvenient and not practical, since while it solved one problem it neglected other considerations and therefore often resulted in the creation of other problems.
Extensible or telescopic pipe joints and/or nipples for the above purposes have been proposed and produced in the past, but these prior devices were not especially satisfactory for the reason that they involved additional parts of a type which added considerably to the expense. The fabricating cost of the parts was not only considered commercially uneconomical, but the assembly expense was considerable as well as material costs.